Drying Behaviour and Kinetic Modelling of Shweta and Purple Guava (Psidium guajava L.) Leaves under Various Drying Techniques

Guava is a delicious fruit loaded with essential nutrients; in addition, its leaves are equally beneficial. It contains various nutritional and bioactive compounds that offer a range of health benefits and can be used as a complement to medicines. The experiments were carried out and replicated thrice to evaluate the concentration of bioactive compounds in the dried leaves. Guava leaves were dried in shade under ambient conditions as well as using tray (50°C, 60°C and 70°C) and microwave drying (360 W, 540 W and 720 W). To explain the drying process, nineteen available models were evaluated for the best fit. The drying data were best explained by the Page model and Verma model in shade drying; Midilli and Kuck model, as well as the Jena and Das model at 700C tray drying; Midilli and Kuck and Logarithmic model for 360 W microwave drying of Purple guava and Shweta guava, respectively. In both guava varieties, L*, a*, b* values were higher in fresh leaves in comparison to shade, tray and microwave dried leaves. The flavonoid contents for fresh Purple and Shweta guava leaves were 49.81 and 31.71 mg QE/ mg dry weight, respectively in comparison to 208.62 mg QE/mg dry weight & 84.79 mg QE/mg dry weight for Purple and Shweta dried leaves.